The invention relates to a method of repairing in situ a transport or distribution pipe of thermo-fusible material inside which a fluid such as water or gas is carried, as well as a device for repairing in situ a pipe of thermo-fusible material.
The invention also relates to a method of repairing in situ a tank of thermo-fusible material in which a fluid such as water or gas is stored, as well as a device for repairing in situ such a tank.
The invention therefore relates to the field of repair work on a damaged section of a pipeline or pipe of thermo-fusible material or on a tank of thermo-fusible material, in which pipe or tank a fluid is carried or is stored. Said fluid can be flammable and/or explosive. It can also be under pressure. For example, it can be natural gas.
The great majority of distribution systems, particularly as concerns the distribution of city gas or natural gas, are composed of pipes or tubes of polyethylene or polyamide, polybutylene, polypropylene or polyvinylchloride. To assemble such tubes, there are several existing techniques. For example, one consists of heating the ends of two tubes placed facing each other until the thermo-fusible material is sufficiently fluid so that the two ends, pressed lightly against each other, fuse together and form a joint that is appreciably sealed to the gas and with a mechanical strength compatible with the use of the pipes to be formed.
This assembly technical can also be applied, in a similar way, to form a tank from elements made of thermo-fusible material.
Pipes and tanks of thermo-fusible material, which have been used in France since the middle of the 1970s, show good resistance of this material over time, at least with respect to piping in gas distribution systems. However, because of possible accidental damage to these pipes and tanks, it is necessary to have methods of in-situ repair that avoid, in so far as possible, the systematic complete replacement of a damaged section of a pipe or the complete replacement of a tank that would seriously affect the operation of the system.
To simplify the reading of the following text, and to make it easier to understand, the present invention will be described below only in reference to pipe of thermo-fusible material, although this does not indicate a limitation of the field of application to this sole example.
Pipe of thermo-fusible material can be damaged in different ways. One such way results from a puncture of a section so that it is no longer impervious. In this situation, the complete replacement of the section is nearly inevitable.
Another way causes internal or external damage of the pipe, although it remains impervious for the short term (external cracks or gouges, creation of internal micro-fissures by a repair operation by partially flattening the pipe).
Currently, in order to attempt to repair such pipe, within the scope of a repair operation by partially flattening, an electrically weldable reinforcing saddle is installed, the purpose of which is only to locally reinforce the damaged area and the welding of which can be tricky because of the ovalization of the pipe.
For economic and technical reasons, the installation of a reinforcing saddle is not used to repair external damages (such as a gouge).
With respect to said gouges, the generally accepted threshold for damage is around 10% of the wall thickness for pipe under pressure, for example.
However, the current lack of knowledge of how the accuracy of this value affects the reduction in service life of damaged pipe does not allow all borderline cases to be handled confidently, that is, those cases in which the depth of the defect is very close to the aforementioned value.
The object of the invention is to propose a method of repairing in situ a pipe or tank of thermo-fusible material, that is simple to implement, does not result in special expenses and which makes it possible to obtain a reliable and durable repair of a section of pipe or a damaged tank that could avoid having to systematically replace the whole section or the damaged tank.